Apparatus for the manufacture of plastic explosive pellets



9 1954 E. G. GUENTHER ETAL 2,666,948

APPARATUS FOR THE MANUFACTURE OF PLASTIC EXPLOSIVE PELLETS Filed July16, 1943 2 Sheets-Sheet 1 Edfl'ar' G- Guenther Robert E. Burton amenW010 I 1954 E. G. GUENTHER ETAL 2,666,948

APPARATUS FOR THE MANUFACTURE OF PLASTIC EXPLOSIVE PELLETS 2Sheets-Sheet 2 Filed July 16, 1943 Patented Jan. 26, 1954 UNITED PATENTF 'F l CE Application July '16, 194$,Seri'al No. 495,084

101mm. 1 .Ihepresent invention relates g'enerallyto thermoplasticexplosive compositions, and more particularly to an improved apparatusfor casting andvpelleting the same.

Heretofore it has been common practice in manufacturing high explosivesto produce "a flaked, grained, crystalline or-other free-flowingmaterial which can be safely charged into'agitated mixing vessels havingclearances of less than 1 inch. When pellets of single explosivespelletsof a size and shape whlchcanb'e remelte'd quickly and safely, and"which can he used "directly for pellet loading.

. Another object is the "p'rovisic'mor apparatus for producingfree-flowing pellets from thermoplastic explosive compositions.

Other objects andadvantages willbe apparent as the invention ishereinafter-more 1 particularly described.

A preferred illustrative embodiment of the present invention is shown inthe appended-drawing, wherein:

Figure 1 is-a side 'elevation of the p'e'lleti'ng apparatuszas-a whole;

Figure 2 is a sectionongtheimes z ofFigure '1;

Figure Sis a plan -of the extrusion vessel, the direction of beltmovement and the pellet rows being indicated by the arrow and the dottedlines, respectively;

Figure 4 is a vertical cross section of the extrusion vessel shownin'Figure 3;

Figure 5 is a perspective view of an agitator for the extrusion vessel;

Figure 6 is a perspective view-of the scraper and apron atthedischar'geend of the apparatus shown in Figure 1-; and

Figure 7 is a perspective view of one of the formed pellets.

Referring particularly to Figure l, the apparatus comprises a machinebed or frame I supporting at each end, a rotatably mounted pulley wheel2 and 3,"o'ne-of which (2) isdriven in any suitable-manner, for exampleby means offabelt 2a passing-over pulley 2b. The two wheels-2 "and '3carry'an'endless metallic belt 4 preferably made of stainless steel.Suitable supporting skids 5, preferably of wood, on the underside of theadvancing belt-prevent the belt'fromwibrating'ahtl thereby obviate-theformation of disc' 'shapedpellets. The under side of the returningbeltis supported by idle rollers 6, and a swinging 'belt "tightenerroller Ga may be provided on 1 the 1 upper side ofthe returning belt. u

At the feed and of the be1t ,-a'steam jacketed ex- 'trusion kettle issupported a "suitabledistance above the beltl, onhkettlepracket-B. Thdis- "tance of the kettle I -'ahove-the-belt"4 is so ad- 'iusted thatuniform droplets of explosive will'forin during the period of fall fromthe kettle to the belt.

The details of 'thelkettle are morefparticularly shown in Figures 3, 4and 5. The kettle consists of two concentric 'n'e sted pots 20 and 2 lsuitably united to form a single jacketed vessel. Suitable 'outlet andinlet ports 22 and 23 permitstearn to be introduced into theannular"spacebetween the pots Hand 21. The bottom of the-pot'is providedwith "a number of extrusion holes, 2'4, uniformly spaced'and'arranged inthe form of a circle which ar'e'also steam jacketed, as shown, the holesbeing so located as to provide a uniformly -spaced feed. Atwisted-anchor agitator 25 provided with upturned ends 26 is connectedto a hub 21 which has a socket connection with drive shaft 28, so thatthe pot contents maybe stirred duringpper ation. 5 Set screw ZSsecureshub-21 to drive shaft 28. Shaft 28 is rotatably supported in theupright- 12 (Fig.1) and adapted'to be'rotatedbythe pulley wheel Hconnected 'through'a V=be1t (not shown) to a suitable source for power-(not shown) for slowly rotating the agitator-shaft 28,

Above and below the advancingb'elt'li are disposed. suitable air ducts12 and 13 provided with spaced air outlet slots!!! on the face adjacentto the advancing some that cool 'ainmayb'e blown against the upperandlowe'r surface-thereof. "Ifhe ducts I2 *and I3 are connected throughconduits and [5 to air trunk a! which isconnectedivith a suitablepressure Tan (not shown).

At the discharge end or the "belt, a 'wooden scraper blade 11 isprovided to remove anyexplosive pellets which adhere to the belt 4. Theexplosive pellets fall into a suitable hopper H, being collected on theapron l8 which desirably consists of; a frame covered with cloth 32 tocushion the fall.

In operation, the plastic explosive is placed in the steam jacketedextrusion vessel I wherein a constant level is desirably maintained inorder to obtain drops of uniform volume. As the agitator 25 revolves,the plastic flows through the extrusion holes 24 and falls in the formof discrete globules 9 through the air onto the advancing belt 4. As thedeposited droplets, supported on the belt, are carried forward betweenthe upper and lower air ducts l2 and I3, they are gradually solidified.When the pellets reach the discharge end most of them slide onto theapron 18 or directly into the hopper l 6. Any pellets which adhere tothe belt are removed by the scraper blade I! and thence fall into thehopper It.

By suitable adjustment of the plasticity of the explosive, the size ofthe extrusion holes 24, the depth of the plastic in the extrusion vessel1, the height of the fall from the extrusion vessel 1 to the belt l, thecooling rate, the length of the belt etc., the explosive may be obtainedin pellets of varying size and shape. Generally the pellets, inconfiguration, resemble an unopened rose bud, as shown in Figure '7, andare freeflowing.

As an example of the preparation of an explosive composition that may beformed into pellets according to the present invention, the following isgiven:

One hundred parts by weight of water is placed in a steam-jacketedmixing vessel provided with an efiicient stirrer and equipped with ahood for removing TNT fumes. 400 parts by weight of TNT is then addedand the mixture agitated until the TNT is completely melted (15 poundsof steam pressure being applied in the jacket). After allowing themixture to come to rest, the water separates and rises to the top of themolten TNT. About 705 to 750 parts by weight of moist cyclonite (15-20%moisture, corresponding to 600 parts of cyclonite on a dry basis) isthen added slowly through the water layer which appears to disperse thecyclonite and permit rapid mixing with the TNT. After the cyclonite isall added, the mixture is stirred for about one-half hour and the waterlayer then decanted. Heating is continued for about one and one-halfhours in order to vaporize all the water from the molten mass. Duringthe foregoing operations, 15 pounds steam pressure is maintained in thejacket until the temperature of the molten composition reaches about 104C. Thereafter, the steam pressure in the jacket is reduced to aboutpounds. By holding the molten composition about 104 C., is was foundthat the subsequent operation of wax incorporation is facilitated.

After the water is substantially completely removed from theTNT-cyclonite composition, 1% of a previously melted amorphous petroleumwax, for example Aristowax sold by Union Oil Co. of California, is mixedwith the TNT-cyclonite mixture in the mixing vessel, while maintaining amixture temperature of 104 C.

Preferably an agent for lowering the interfacial tension between thecyclonite and the amorphous wax is added to the amorphous wax before itis added to the TNT-cyclonite mixture. For this purpose a large numberof long chain hydrocarbon derivatives containing polar groups (e. g.,carbonyl, carboxyl, hydroxyl, etc.) may be used.

The long chain fatty acids such as stearic acid, for example, areillustrative of the type of interfacial adjuncts which are suitable. Itis preferred, however, for economical and other reasons, to employ thecrude mixture of polar compounds obtained by bubbling air through heatedpetroleum hydrocarbons (e. g., those derived from Pennsylvania crudes)in the presence of oxidation catalysts such as manganese oleate. Theresulting water insoluble, oil-soluble, oxygen-containing petroleumderivatives consist of alcohol. ketone and carboxyl compounds as well asesters and probably some lactones, etc. These complex mixtures areavailable on the market under the trade name Alox, such as Alox-310,A101:- 350 and Alox-600. Alox-600 to the extent of about 10% by weightof the amount of the amorphous petroleum wax used is added to said waxbefore it is added, as above described, to the TNT-cyclonite mixture.

The proportion of cyclonite in the above described explosive compositionmay be varied, as will be understood by the person skilled in the art,and indeed, in some instances it may be desirable to increase theproportion of cyclonite to 62-63% by weight of the composition, in orderto obtain a more workable composition.

The cyclonite referred to above is an explosive which has a molecularformula of CsHsOsNe, and a melting point in the pure state ofapproximately 205 C. It is considered to becyclotrimethylenetrinitramine, and may be prepared by the methoddescribed by Hale in the Journal of the American Chemical Society, vol.47, page 2754, issued in 1925.

In the foregoing detailed description, it will be apparent that manyvariations may be made without departing from the spirit and scope ofthe invention. We therefore intend to be limited only in accordance withthe following patent claim.

We claim:

An apparatus for the manufacture of uniformly sized and shaped highexplosive pellets comprising an extrusion chamber having its sides andbottom surrounded by steam jacketing forming therewith a steam spacehaving inlet and outlet connections thereto, bottom openings in saidchamber connected by pipe portions leading through said steam space andsaid jacket, a rotatably mounted S-shaped anchor agitator havingupturned ends, said agitator cooperating with said pipe portions to movea plastic explosive composition therethrough, a flexible conveyormounted beneath said chamber for receiving and moving said extrudedmaterial, supporting means for dampening the vibration of said conveyorwhile in motion, and means for cooling said ex-' truded material on saidconveyor.

EDGAR G. GUEN'I'HER. ROBERT C. BURTON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 450,591 Schrader Apr. 14, 1891 1,455,923 Minniberg May 22,1923 1,469,316 I-Iartshorn Oct. 2, 1923 2,088,247 Paton July 27. 1937

